1. Field of the Invention
This invention relates to loom improvements which enable the loom heddle frames to be positioned as close as possible to the shed vertex or fabric formation line as is compatible with the size only of the swinging reed while maintaining a minimum thickness of the leno-weaving device, of an independently driven type, within its region of operation, hence resulting in a considerable reduction in mechanical stresses on the heddle frame drive members, the achieving of a cleaner shed and hence a higher loom efficiency, and the possibility of forming fabrics of greater width on the same loom.
2. Discussion of the Background
As is well known, in looms it is always sought to position the heddle frames as close as possible to the shed vertex or fabric formation line, i.e., basically as close as possible to the rear dead center of the swing of the beating reed, such an arrangement resulting in considerable advantages.
In this respect, the shorter travel required of the heddle frames for equal shed opening angles results in evident reduced stresses in the warp yarns and lower mechanical stresses on the drive members of said heddle frames, with obvious economical and operational advantages. Again, the consequent reduction in length of the warp yarn portions extending from the heddles of the heddle frames to said shed vertex or fabric formation line results in reduced elastic yielding of said yarn portions, ensuring a more effective and immediate separation of any adjacent warp yarns stuck together, with the advantage of a cleaner shed and a consequent increase in loom efficiency.
However, to prevent unravelling of the fabric under formation, its edges are generally protected by a leno-weave obtained by a suitable device.
Various types of leno-weaving device are already known in the state of the art.
In one of the known types, the two links of the device are inserted into the first two heddle frames of the loom and are alternately lowered and raised by said two first heddle frames respectively.
Although this arrangement reduces weft wastage to a minimum in that the thickness of the device within the operating region is a minimum and also enables fabrics of greater height to be formed on the same loom, it has the serious drawback, by using the first two heddle frames for its drive, of inevitably moving the position of the operating heddle frames rearward from said shed vertex or fabric formation line, with evident negative consequences in the light of the foregoing. A further drawback is the need to use and keep in movement the said two heddle frames only for operating the leno-weaving device, with a consequent increase in the total number of heddle frames and hence in mechanical stresses.
To obviate this drawback, independently driven leno-weaving devices have been used, namely devices comprising two links which are slidable along a suitable central member and are alternately raised and lowered by separate drive members other than heddle frames or false selvedge forming devices.
Such independently driven leno-weaving devices have however to be interposed between the swinging reed and the first heddle frame, hence introducing the said drawbacks due to the necessary positioning of the operating heddle frames rearwardly from said shed vertex or fabric formation line. Again, the presence in said independently driven leno-weaving devices of self-contained drive members and their specific construction means that some of said known devices have a considerable thickness within the region of operation, with consequent weft wastage.